The present invention relates to a process for the adhesion of a flat plastic substrate in the form of a circular disk to a like second substrate, for example for the fabrication of a digital video disc and apparatus for implementing the process.
A holding apparatus is known for the transport and processing of a flat substrate in the form of a circular disk (DE 295 12 381), in particular of a CD or CD-ROM, consisting of a housing with a central chamber which can be connected to a pressure source. A plurality of suction cups of an elastic material are connected to the chamber via suction channels and distributed over the chamber wall turned toward the substrate. Several dosing nozzles corresponding to a distribution channel are provided in the housing, ending approximately in the plane of the suction cups, and extending parallel to the suction channels where the distribution channel is provided with an attachment for connection to a paint source.
Furthermore an apparatus is known for the lacquering of a flat substrate in the form of a circular disk (DE 295 12 500), in particular a CD, which consists of a motordriven plate rotatable about a vertical axis for holding the substrate, a lacquer dispenser disposed above the plate which has an annular collar revolving with and enclosing the plate and partially connected to it with studs, and a positionally fixed housing with an annular edge part engaging the collar from outside. The collar is formed of two portions, of which the one portion is formed as a sleeve forming a straight frustum of a cone which, enclosing the plate, extends from its radially outer edge a bit upward. The other portion of the collar is formed as a sleeve forming a straight frustum of a cone which, enclosing the plate, extends from its radially outer edge downward so that the inner wall of the upper collar plate tapering upward collects particles of paint cast off in the radial direction and upward by the plate rotating about its vertical axis and lets them run off via recesses formed by the studs in the radial outer edge area of the plate at the inner wall of the lower portion of the collar tapering downward.
A process for the partial removal of thin layers of a substrate is also known (DE 42 02 194) in which a preferably plane surface of the substrate provided with a thin layer, for example a lacquer or metal layer or the like, is set in rotation about a perpendicular axis to the surface, and a solvent or etching agent is applied to the edge area of the surface which is cast off from the substrate by centrifugal force carrying with it the dissolved or etched off layer area. The surface of the layer area to be removed is at least partially masked by means of a template which possesses an inner contour corresponding to the layer to be removed and is disposed for the formation of a capillary at a small distance from the surface, that, with feeding of solvent or etching agent, the template is set in rotation synchronously with the substrate at a definite speed of revolution. After a definite time the feeding of solvent or etching agent is stopped and the solvent or etching agent along with the dissolved or etched off layer area is cast off at an appropriately increased speed of revolution.
Moreover an apparatus for grasping and holding a flat substrate, preferably in the form of a circular disk, with a central opening, for example a compact disc, is known (DE 195 29 945). It includes several finger-like grasping elements tiltably situated in the housing wherein the grasping elements are held and guided in openings or apertures in the head portion of the housing. This permits tilting motions of the grasping elements about axes transverse to the longitudinal axis of the housing, wherein the tilting axes of all grasping elements extend in one plane and form together one polygon enclosing the longitudinal axis. Magnets are fixedly disposed at each end of the grasping elements turned away from the substrate which work together with an electromagnet provided in the housing above the magnets whose magnetic field axis coincides with the longitudinal axis of the housing and which moves the ends of the grasping elements provided with magnets back and forth between two stops according to the polarity of the electromagnet.
Finally an apparatus for the transport of digital video discs from initial stations formed as carousel transport apparatuses over several process stations to final stations has been proposed (DE 197 29 525.8) wherein the process stations cause the processing, for example, layering, checking, sorting, and gathering of the substrates and wherein grasping arms with grasping elements or suction lifters make possible the further transport of these substrates from station to station. A motor drive unit with a swivel apparatus and two lifting apparatuses are provided which can be driven separately and which work together with manipulators or grasping arms. The drive with grasping arms forming the conveyance station is disposed at the same distance from several stations, for example the preparation station, the lacquering/gluing station, the return conveyance station, and the testing station. The two lifting apparatuses of the motor drive unit simultaneously execute with their grasping arms the same and/or different lifting motions (vertical motions) and swiveling motions superimposed on these or subsequent to them.
An object of the present invention is to provide a process and an apparatus for its implementation according to which two plane substrates for a digital video disc can be adhered to one another without blisters and uniformly and in fact in such a way that the layer of adhesive hardening between the two discs is of equal density and composition throughout and for this purpose is distributed uniformly over the entire surface of the substrate before hardening.
A further object of the present invention is to specify a process and an apparatus for the transport of digital video discs.